Various side rails for beds have been proposed hitherto. Among them, widely used are foldable side rails, each comprising multiple strut members pivotally rotatably connected between an upper crosspiece member and a lower crosspiece member, to form a parallel link mechanism, in such a manner that the side rail can assume a deployed state for use where the abovementioned strut members are held in an upright position and a stowed state of disuse where the strut members are laid down to lower the upper crosspiece member in parallel. The upper crosspiece member of such a foldable side rail is desired to be kept as low as possible in height in the stowed state of disuse, lest the upper crosspiece member should interfere when the person lying on the bed leaves from the bed or when a care giver extends assistance to the care receiver on the bed. To meet this requirement, it is only required that there are no clearances at all or there are the smallest possible clearances formed between the multiple strut members overlapping one after another in the stowed state.
However, if an operator (user) or a third party puts his/her finger between the strut members unconsciously for folding the side rail into the stowed state, or if an operator (user) or a third party applies a load to the upper crosspiece member while another person puts his/her finger between a clearance formed due to any foreign matter such as a mattress held between the strut members in the stowed state, the finger can be caught between the strut members very dangerously.
To avoid such a danger, for example, Patent Document 1 proposes a constitution in which when a side rail is folded to a state just before the stowed state is reached, holding pieces installed on the lower crosspiece member hold the strut members for preventing the strut members from being further laid down and remain urged toward the holding position by springs.
In this constitution, when the strut members have been laid to a state just before the stowed state is reached, the strut members are brought into contact with and supported by the holding pieces kept in the holding position by the springs, and since spaces with a predetermined width still remain to be formed between the respective strut members at this position, no finger can be caught between the strut members.
After the strut members are once held at the holding position, the holding pieces can be further pivotally rotated against the urging of the springs, to leave the strut members supported in a non-holding position by a person, and thus since the strut members can now be pivotally rotated again, the strut members can be further laid down to the stowed state.    Patent Document 1: Japanese Patent 2697765